6.6-stable review patch. If anyone has any objections, please let me know.
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From: Vladimir Oltean vladimir.oltean@nxp.com
[ Upstream commit da62abaaa268357b1aa66b372ace562189a05df1 ]
When using the SGMII PCS as a fixed-link chip-to-chip connection, it is easy to miss the fact that traffic passes only at 1G, since that's what any normal such connection would use.
When using the SGMII PCS connected towards an on-board PHY or an SFP module, it is immediately noticeable that when the link resolves to a speed other than 1G, traffic from the MAC fails to pass: TX counters increase, but nothing gets decoded by the other end, and no local RX counters increase either.
Artificially lowering a fixed-link rate to speed = <100> makes us able to see the same issue as in the case of having an SGMII PHY.
Some debugging shows that the XPCS configuration is A-OK, but that the MAC Configuration Table entry for the port has the SPEED bits still set to 1000Mbps, due to a special condition in the driver. Deleting that condition, and letting the resolved link speed be programmed directly into the MAC speed field, results in a functional link at all 3 speeds.
This piece of evidence, based on testing on both generations with SGMII support (SJA1105S and SJA1110A) directly contradicts the statement from the blamed commit that "the MAC is fixed at 1 Gbps and we need to configure the PCS only (if even that)". Worse, that statement is not backed by any documentation, and no one from NXP knows what it might refer to.
I am unable to recall sufficient context regarding my testing from March 2020 to understand what led me to draw such a braindead and factually incorrect conclusion. Yet, there is nothing of value regarding forcing the MAC speed, either for SGMII or 2500Base-X (introduced at a later stage), so remove all such logic.
Fixes: ffe10e679cec ("net: dsa: sja1105: Add support for the SGMII port") Signed-off-by: Vladimir Oltean vladimir.oltean@nxp.com Link: https://patch.msgid.link/20251122111324.136761-1-vladimir.oltean@nxp.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/dsa/sja1105/sja1105_main.c | 7 ------- 1 file changed, 7 deletions(-)
diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c index 0de73a6257f9a..1acc5d912d161 100644 --- a/drivers/net/dsa/sja1105/sja1105_main.c +++ b/drivers/net/dsa/sja1105/sja1105_main.c @@ -1307,14 +1307,7 @@ static int sja1105_set_port_speed(struct sja1105_private *priv, int port, * table, since this will be used for the clocking setup, and we no * longer need to store it in the static config (already told hardware * we want auto during upload phase). - * Actually for the SGMII port, the MAC is fixed at 1 Gbps and - * we need to configure the PCS only (if even that). */ - if (priv->phy_mode[port] == PHY_INTERFACE_MODE_SGMII) - speed = priv->info->port_speed[SJA1105_SPEED_1000MBPS]; - else if (priv->phy_mode[port] == PHY_INTERFACE_MODE_2500BASEX) - speed = priv->info->port_speed[SJA1105_SPEED_2500MBPS]; - mac[port].speed = speed;
return 0;